High-speed amplitude electro-optical modulators (AEOMs) are necessary components in a growing number of applications, such as wireless communication, electronic warfare, etc. A method for intensity modulation in AEOMs, according to the prior art, is to apply electronic signals to control the refractive index of a waveguide made from electro-optically active materials and shift the phase of one of the interfering beams of a Mach-Zehnder interferometer.
The prior art relevant to the proposed method is described in a recent book by N. Dagli “High-speed photonic devices,” Press, 2007, Chapter 3; U.S. Pat. No. 6,640,020 (S. Ionov, “Method and apparatus for electro-optic delay generation of optical signals,” U.S. Pat. No. 6,640,020, October 2003); and the review by J. Hukriede, D. Runde, D. Kip, “Fabrication and application of holographic Bragg gratings in lithium niobate channel waveguides,” J. Phys. D: App. Phys. v. 36, pp. R1-R16, 2003, the entire content of all three of which is incorporated herein by reference.
The basic disadvantage of previous devices is that a high driving voltage is required for a π-phase shift in the AEOM and complete elimination (or destructive interference) of the transmitted optical signal. Therefore, there is a need for a low-driving voltage high-speed AEOM.